Celltjlosic material



process for treating cellulosic material Patented Oct. 6, 1936- PATENT OFFICE 2,056,810 CELLUDO SIC MATERIAL Frederic H.

to General New York Smyser, Marblehead, Mesa, assignor Electric Company, a corporation of No Drawing. Application September 13, -1934,

' Serial No.

9 Claims.

The present invention relates to an improved and in particular waste cellulosic material such gasse and the like. in order to convert it into useful products and to the products produced thereby. More particularly the present invention is an improvement over the process described in my prior Patent No. 1,792,254 which is assigned to the assignee of the present invention.

In accordance with the process my prior patent above referred to comminuted cellulosic material such as waste bagasse, sawdust, cornstalks and the like is first treated under heat and pressure with an alkali such as sodium hydroxide whereby resinous substances formed from the natural constituents of the cellulosic material are caused to be intimately intermingled with the fibers thereof and then an acid such as sulfuric acid is added in order to precipitate the resinous substances on and around the fibers.

The mass, after filtering and washing is dried and then molded in a comminuted state in the presence of an alkaline agent.

I have discovered that I can eliminate the addition of the acid in order to precipitate the resinous substances on the fibers by controlling the original cooking of the cellulosic material. I have found that by carefully-controlling the cooking of the material with the alkali solution using an adjusted concentration of the latter a point is reached where the liquor turns sufllciently acid to precipitate the resinous substances on and around the fibers. This does away with the necessity of adding acid and eliminates the necessity of an added handling operation. Moreover, the elimination of addition of acid yields a final product of superior dielectric strength since there is no excess acid to wash out which is always an expensive and uncertain operation. Since the acid is not added to the mass as a separate entity the the filter for the washing operation which is now simpler, faster and less expensive.v i

*In order that my invention may be better understand I cite an example below of myimproved process. It is to, be the example given is merely illustrative of my invention and is not limiting in character. The figures given in the example represent merely a satisfactory balance between the amount of resin as ba-' describedin v understood, however, that formed, toughness of fiber and reasonable operating conditions as will readily be understood by those skilled in the art.

a charge consisting of 1 Pounds Bagasse fiber 10 Caustic soda (sodium hydroxide) 1% Water is placed in a digester which is sealed at atmos- 10 pheric pressure. It is important that there be no leaks in the digester during the cooking operation as either an excess of air or a deficiency of air in the apparatus is detrimental. After sealing, the digester is heated to a temperature of to 15 C. for 18 to 22- hours. The temperature and time of cooking should be carefully observed since the effect of too long cooking or excess temperature will produce too much acid and result in a rottin of the fiber without formation of additional resin. 20 If the above temperature and time is observed it will be found that the liquor in the digester is acid to litmus and the mass is at the end point to be reached.

The mass is now allowed to cool and discharged 25 from the digester, placed in filters and the liquor allowed to drain off. The fiber is washed with water and dried. This fiber contains from 15 to 18% resin.

While it is not necessary to make the second 30 cook about to be described, it is preferred inasmuch as it enables the production of a fiber having a higher ultimate resin content.

The liquor drained from the fiber obtained from the digester is replaced therein and a fresh charge 35 of 10 lbs. of bagasse fiber is added, the digester is sealed and a second cook of from two to four hours is made at the same temperature as in the first case. At the end of this time, the material in the digester is cooled and discharged therefrom, the liquor being drained and discarded. The fiber is thoroughly washed and dried. This fiber contains from 25 to 30% resin. While this lot of fiber may be used separately it is preferred to mix it with the first lot obtained in order to increase the average resin content of the mixed fiber.

I In my prior patent above referred to I molded the fiber in the presence of an alkaline agent. In the present improvement I have found it ad- 50 vantageous to employ in place of the alkaline agent a heat convertible synthetic resin and preferably a water soluble phenolic resin prepared in the presence of an alkaline catalyst, for example, sodium carbonate (NazCOa) or hydroxide (NaOH).. By employing such a resin I am able to materially increase the water resistance, me-

' chanical strength and dielectric properties of the der to effect such improvements.

finishedproduct. Moreover, I do not need to employ a very large quantity of the resin in or- Usually from to is suflicient.

The fiber so prepared may be molded under heat and pressure employing the usual ranges of of cost or other factors, to omit the addition of resin to the prepared fibers before molding. The

. exercised, however, in cooling-the mold before the material after treatment in the digester, and washing and drying, may be comminuted or powdated and molded directly without the addition of any other substance whatever. Care must be piece is removed therefrom.

If laminated material is desired, the prepared fiber, i. e., the fiber which has been taken from the digester and washed, is run into a beater, rod

mill or other suitable apparatus where the fiber is prepared for a paper or board machine, and then sheets formed. according to standard paper or board making practice, after which the sheets are dried, laminated and molded. Any thickness of Letters Patent in the United States:

' pounds therein by treating the cellulosic material with alkali solution 01' adjusted concentration sheets may be molded employing the usual temperatures and pressures requisite for such operations. Since no thermosetting resins are employed it is essential that the board be cooled inv the pressbefore withdrawal therefrom. If, however, the fiber having the water soluble phenolic resin added thereto is used athermosetting sheet may be made.

If desired a laminated product of the type described and claimed in Kienle and Scheiber Patent No. 1,921,757 may be made by following the procedure therein. described for utilizing the fiber produced in accordance with the present invention.

What I claim as new and desire to secure by 1. A process for making a molded product from cellulosic material containing natural substances capable of yielding resinous compounds therein, which comprises digesting said cellulosic material with an alkali solution of adjusted concentration 'ata temperature and for a time such that the alkali isv neutralized and until an acid reaction to litmus'is obtained and there is" caused to precipitate on and around the fibers of the material certain resinous and resin forming constituents, separating the solid constituents, washing and drying-the same, adding a synthetic resin, and

' moldingthe mixture under heat and pressure.

2. A process for making a molded product .which comprises preparing resinous compounds .from waste cellulosic material containing natural substances capable of yielding resinous comat a temperature and for a time sufiicient to neutralize the alkali and to convert the liquor of the. mass from the alkaline to the acid side, washing, drying the mass so obtained, intimately mixing therewith a phenolic resin and molding under heat and pressure.

3. A process of making a molded product from waste cellulosic material having natural substances capable of yielding resinous compounds therein which comprises treating such material solely with alkali solution of adjusted concentration under heat and pressure and at a temperature and for a time suflicient to neutralize the alkali to cause the resinous derivatives thereof to waste cellulosic material containing natural substances capable .of yielding resinous compounds therein which comprises digesting said material with alkali solution of adjusted concentration under conditions of heat and pressure-and at a temperature and for a time sufiicient to neutralize the alkali and to precipitate certain-resinous substances formed therefrom on and around the fibers of the material, adding a phenolic resin to the mass before molding-and molding under heat and pressure.

5. A process for making a molded product which comprises the steps of digesting with caustic soda solution of adjusted concentration a cellulosic material having natural substances capable of yielding resinous compounds therein until the dissolved resinous constituents are precipitated therefrom, filtering and washing the mass until it is neutral, drying the same, adding .to the dried mass 9. water soluble phenolic resin,

reducing the entire mass to powdered form, and molding under heat and pressure.

6. The process of forming into a moldedprodnot a comminuted cellulosic material having natural substances capable of yielding resinous compounds therein, which consists in digesting the cellulosic material with alkali solution of adjusted concentration. to dissolve the binding substances and separate the cellulose fibers from each other, continuing the digesting operation until the liquor has become acid and there hasprecipitated on and within the mass of fibers resinous and resin-forming substances, removing soluble by-products, adding a synthetic resin an molding under heat and pressure.

7. A process which comprises heating cellulosic material containing natural substances capable of yielding iresinous substances therein,

in a digester sealed at atmospheric pressure, with an alkali solution of adjusted concentration for a time and at a temperature sufiicient to to an acid reaction to litmus whereby the resinous substances formed from the natural substances of the cellulosic material are conoenanalkali solution of adjusted comentration for a time and at a. temperature 'sume'ient "to :neuztralize the alkali and to convert the liquor to an acid reaction to litmus whereby the resinous substances formed from thena'tura-l tsubstances neutralize the alkali and, to. convert the liquor :in aidigester sealed at atmospheric pressure w'ith of the cellulosic material are concentrated ex-v 75,

ternally on andaround the cellulosic fibers. cooling the mass, separating the fibers by removal of the liquor therefrom, digesting another batch of similar type cellulosic ,material with said liquor for a period considerably shorter than the first period of digestion, cooling the mass, separating the digested fibers, washing apddrying the latter and combining it with the 'first batch of treated fibers, mixing a heat convertible phenolic resin therewith, and heating under pressure in a close die.

9. A process for making a laminated molded product which'comprises digesting cellulosic madrying the sheet, and molding under heat and 10 pressure the desired number oi laminations of said sheet.

If'REDERIC H. BMYSER. 

